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Mimicking the hair surface for neutron reflectometry
Serena Cozzolino1,2, Philipp Gutfreund2, Alexei Vorobiev2,3
1Division of Surface and Corrosion Science, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden. mark@kth.se.
Soft Matter
|September 18, 2024
Summary
Neutron reflectometry reveals how hair care ingredients adsorb to healthy and damaged hair surfaces. Anionic surfactants unexpectedly bind to damaged hair, offering a new way to protect hair without cationic agents.
Area of Science:
- Surface science
- Materials science
- Cosmetic science
Background:
- Human hair surface is hydrophobic due to a lipid layer, primarily 18-methyleicosanoic acid (18-MEA).
- Hair damage removes this lipid layer, exposing hydrophilic, negatively charged surfaces.
- Understanding hair surface interactions is crucial for sustainable and high-performance cosmetic products.
Purpose of the Study:
- To investigate the adsorption of hair care ingredients onto healthy and damaged hair models.
- To elucidate the role of lipid structure and surface charge in ingredient adsorption.
- To demonstrate the utility of neutron reflectometry for characterizing complex hair-surface interactions.
Main Methods:
- Utilized neutron reflectometry (NR) with scattering contrast variation.
- Created three hair-mimetic surfaces: two healthy hair models (varying lipid structure) and one damaged hair model (negative surface charge).
- Studied the adsorption of hair-care ingredients onto these model surfaces.
Main Results:
- Lipid structure, specifically a methyl branch in 18-MEA models, showed minimal effect on ingredient adsorption.
- Unexpected adsorption of an anionic surfactant to a negatively charged damaged hair surface was observed.
- This adsorption facilitated the delivery of neutral components, forming a protective film.
Conclusions:
- Neutron reflectometry is a feasible technique for characterizing complex adsorption on hair surfaces.
- Anionic surfactants can form protective films on damaged hair without requiring cationic agents.
- Findings offer a novel approach for developing targeted hair protection treatments.
